Electric switch mechanism



May 8, 1934. w. w. WILLIAMS ELECTRIC SWITCH MECHANISM Q Original FiledAug. 8, 1952 INVENTOR. MAL TER w. w/u I'm r5 BY M J A TTORNEYS.

Patented May 8, 1934 ELECTRIC SWITCH MECHANISM Walter W. Williams,Bloomington, Ill.

Original application August 8, 1932, Serial No. 627,861. Divided andthis application August 14, 1933, Serial No. 685,023

2 Claim.

This invention relates to electric switches and more particularly to athermally actuated switch mechanism particularly adapted as a control inan electrically operated fluid fuel heating system,

5 but may be employed wherever it is desirable to control an electriccircuit or operate an electric switch by temperature changes.

It is an object of this invention to provide mechanism responsive totemperature changes for opening and closing an electric switch which issimple and positive in its operation. It is a further object of thisinvention to provide 'a reciprocating actuating element for throwing theswitch from one extreme position to the other and thereafter allowfurther movement of the actuating element in the same direction withoutany undue strain upon the switch operating mechanism and immediatelythrow the switch to the other position upon movement of the actuatingelement in the opposite direction.

This application is a division of this applicants prior co-pendingapplication Serial Number 627,861 filed August 8, 1932, Electric switchmechanism.

With these and other objects in view, reference is made to theaccompanying sheets of drawing which illustrate a preferred form of thisinvention with the understanding that minor detail changes may be madewithout departing from the scope thereof, and that while an embodimentof this invention is illustrated as applied to a stack safety, it is notlimited to this single use.

In the drawing;

Figure l is a view in front elevation of the insulated switch carryingplate, with cover removed, illustrating the positions assumed by thecontacts when operated by the actuating arm at the end of its travel inone direction. I

Figure 2 is a similar view illustrating the positions assumed by thecontacts when operated by the actuating arm in an intermediate position.

Figure 3 is a similar view illustrating the positions assumed by thecontacts when operated by the actuating arm at the other end of itstravel.

Figure 4 is a top plan view, with parts broken an embodiment isillustrated upon the accompanying drawing. As shown, the switchmechanism is mounted upon an insulated plate 1 carried within the casing2 preferably provided with a removable front plate 3 and with a tubularex- Q0 tension 4 extending from one side thereof adapted to be receivedwithin the tubular portion of a bracket adapted to be secured to thestack of a furnace, or adapted to be passed through and secured to anend wall of a casing 5 secured at one side of the draft pipe 6 of an oilburner, which casing extends within the combustion chamber 8 and at itsrear end communicates by passageway 7 to the interior of the draft pipe6, as shown in Figure 4.

An actuating rod 9 is mounted to reciprocate horizontally through thebore of the tubular portion 4. One end of the U-shaped bi-metallicthermal element 10 is secured to the and of the portion 4 extendingwithin the stack, or mounted 7 within the casing 5 shown in Figures 4and 5 to be subjected to theheat of the combustion chamber 8. Theopposite end of the thermal element is attached to the inner end of theactuating rod 9 as by perforating or bifurcating the end of the thermalelement to pass about the actuating rod 9 between horizontal pins 11 onthe actuating rod so that upon expansion and contraction of the thermalelement, a horizontal, longitudinal movement will be imparted to theactuating rod. 35 Commercial oil burners of the type illustrated inFigures 4 and 5 employ a fan blower, not shown, for forcing air underpressure through the draft pipe 6 to mix and form a combustible mixturewith fluid fuel issuing from thenozzle and dis- 9o charging into thecombustion chamber 8. The heat within the combustion chamber isexcessive, and while iii-metallic thermal members, such as 10, have beendeveloped to withstand excessive heat, yet it is preferable to divert aportion of the air when forced through the draft pipe by the blower topass through the opening 7 and over the thermostatic member 10 toprevent the deterioration of the thermostatic material.

In some controls for fluid fuel burners, it is desirable to close onecircuit before the other is open and this particular switch is designedto fulfill this heed. A contact carrying arm 12 in the form of a stripof resilient metal is secured at its upper end by brackets 13 centrallyto the upper end of the panel 1. The end of the actuating rod 9 enteringthe casing 2 is provided with a plurality of teeth 14 upon its upperside and the contact carrying arm 12 is of such length that it willengage between the teeth of the rod 9 as the rod is a a bio actuated bythe thermal element to reciprocate. The contact carrying arm 12 adjacentto its lower end supports the oppositely disposed contacts 15 and 16which are adapted to engage corresponding contacts 1'? and 18 when thearm 12 is in vertical position as shown in Figure 2. The contact 1'1 iscarried upon the lower end of a resilient contact carrying strip 19secured at its upper end by the bracket 20 to the insulated plate id '1.The other contact 18 is carried upon a similar resilient contact carryig strip 21 secured by the bracket 22 to the upper portion of theinsulated plate 1. The contact carrying arm 12 may be connected by aflexible connection 23 to the bindpost 24 at the bottom of the panel 1.The brackets 26 and 22 are connected by wires 25 and 26 to the bindingposts 27 and 28.

Figure 1 illustrates the actuating rod 9 as it approaches one end of itsmovement caused by the contracting oi the thermal member 10. The end ofthe contact carrying arm 12 in engagement the teeth 14 has been swung tothe right so i maintain the engagement between contacts and 17 and hasbroken the engagement bet J33 contacts 15 and 18, thereby completing thecircuit from binding post 24 to the binding Dost Upon further travel ofthe rod 9 in the same direction, the end of the contact carrying arm 12wipe over the teeth as the arm is resilient and t e contact carryingstrip 19 is also resilient. n thermal element 10 ceasing to contractbeginning to expand, the rod 9 will be moved e opposite direction untilit assumes the icai position as shown in Figure 2. Engaget W smaintained between the contacts 16 i? by the resilient strip 19 and thecontacts 15 be brought into engagement. Furmovement in the samedirection will sepacontacts 16 and 1'7, maintaining contacts 15engagement as the contact carrying resilient, as shown in Figure 3. 1onion, the thermal element has apltmit of expansion and the circuit willbe closed between binding posts 24 and 28, while the circuit betweenbinding posts 24 and 27 is broken.

. It is to be noted that the reciprocation oi the actuating rod 9alternately opens and closes the circuits between the binding posts, andin so doing always maintains one circuit closed before the other isopened.

What I claim is:

1. An electric switch mechanism including a reciprocating actuating rodhaving a plurality of teeth forming a rack thereon, means forreciprocating said rack, three electric contacts, one of said contactsmounted upon a movable arm, yielding means adapted to be engaged betweenadjacent teeth of said rack whereby reciprocation I of the rod moves thecontact upon the arm into and out of engagement with another contact toclose one circuit before it opens the other and after said engagementand upon further movement of the rod in the same direction allows theteeth of the rack to travel under the engaging means, and yielding meansto maintain the en gagement oi the contacts when made.

2. An electric switch mechanism including a reciprocating actuating rodhaving a plurality of teeth forming a rack thereon, means forreciproeating said rack including a temperature responsive deviceengaging said rod, a plurality of electric contacts, one of saidcontacts mounted upon a flexible movable arm normally engaged by twoother contacts on each side thereof, said arm having a free end adaptedto be engaged between adjacent teeth of said rack whereby reciprocationof the rod moves the contact upon the arm out oi engagement with onecontact and thereafter upon further movement of the rod in the samedirection allows the teeth of the rack to travel under the engagingmeans, and yielding means to maintain the engagement of the contactsfirst made including a flexible mounting for each :ngaged contact.

WALIER W. WILLIAMS.

